A breathing circuit system for supplying a breathable gas from a breathable gas supply system to a patient interface. A semiconductor device and its manufacture method are to be provided, the semiconductor device having memory cells with a high retention ability and field effect transistors having an insulated gate with large drive current. First, second, and third clock signals of the plurality of clock signals are asynchronous to each other. A tracking mode phase coefficient is determined based on the error signal for use in the PLL during a track a tracking period. An end face of one of plate members adjacent to each other in the closed section is abutted against an inner surface of the other plate member and in this state the abutted portion of the plate members is fillet-welded throughout the overall length of each plate member.